Methods of using thermoplastic polyurethanes in selective laser sintering and systems and articles thereof

ABSTRACT

The present invention relates to systems and methods for solid freeform fabrication, especially selective laser sintering, as well as various articles made using the same, where the systems and methods utilize certain thermoplastic polyurethanes which are particularly suited for such processing. The useful thermoplastic polyurethanes are derived from (a) a polyisocyanate component, (b) a polyol component, and (c) an optional chain extender component; wherein the resulting thermoplastic polyurethane has a melting enthalpy of at least 5.5 J/g, a Tc (crystallization temperature) of more than 70° C., a Δ(Tm:Tc) of from 20 to 75 degrees, where Δ(Tm:Tc) is the difference between the Tm (melting temperature) and Tc.

This application is a Continuation of pending application Ser. No.16/839,394 filed on Apr. 3, 2020, which claims priority from U.S. Pat.No. 1,0647,808 granted on May 12, 2020, which claims priority from PCTApplication Serial No. PCT/US2015/011693 filed on Jan. 16, 2015, whichclaims the benefit of U.S. Provisional Application No. 61/928,430 filedon Jan. 17, 2014, the entirety of all which are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to systems and methods for solid freeformfabrication, especially selective laser sintering, as well as variousarticles made using the same, where the systems and methods utilizecertain thermoplastic polyurethanes which are particularly suited forsuch processing. The useful thermoplastic polyurethanes are derived from(a) a polyisocyanate component, (b) a polyol component, and (c) anoptional chain extender component; wherein the resulting thermoplasticpolyurethane has a melting enthalpy of at least 5.5 J/g, a Tc(crystallization temperature) of more than 70° C., a Δ(Tm:Tc) of from 20to 75 degrees, where Δ(Tm:Tc) is the difference between the Tm (meltingtemperature) and Tc.

BACKGROUND

The present invention relates to solid freeform fabrication and, moreparticularly, selective laser sintering, using certain thermoplasticpolyurethanes.

Solid Freeform Fabrication (SFF) is a technology enabling fabrication ofarbitrarily shaped structures directly from computer data via additiveformation steps. The basic operation of any SFF system consists ofslicing a three-dimensional computer model into thin cross sections,translating the result into two-dimensional position data and feedingthe data to control equipment which fabricates a three-dimensionalstructure in a layer-wise manner.

Solid freeform fabrication entails many different approaches to themethod of fabrication, including three-dimensional printing, electronbeam melting, stereolithography, selective laser sintering, laminatedobject manufacturing, fused deposition modeling and others.

In three-dimensional printing processes, for example, a buildingmaterial is dispensed from a dispensing head having a set of nozzles todeposit layers on a supporting structure. Depending on the buildingmaterial, the layers may then be cured or solidified using a suitabledevice. The building material may include modeling material, which formsthe object, and support material, which supports the object as it isbeing built.

Solid freeform fabrication is typically used in design-related fieldswhere it is used for visualization, demonstration and mechanicalprototyping. Thus, SFF facilitates rapid fabrication of functioningprototypes with minimal investment in tooling and labor. Such rapidprototyping shortens the product development cycle and improves thedesign process by providing rapid and effective feedback to thedesigner. SFF can also be used for rapid fabrication of non-functionalparts, e.g., for the purpose of assessing various aspects of a designsuch as aesthetics, fit, assembly and the like. Additionally, SFFtechniques have been proven to be useful in the fields of medicine,where expected outcomes are modeled prior to performing procedures. Itis recognized that many other areas can benefit from rapid prototypingtechnology, including, without limitation, the fields of architecture,dentistry and plastic surgery where the visualization of a particulardesign and/or function is useful.

There is growing interest in this form of fabrication. Many materialshave been considered for use in such systems and methods using the same,however, thermoplastic polyurethanes have proven difficult to utilize inthese systems and methods. This is due at least in part to thedifficulty in processing the TPU into the proper particle sizedistribution and making sure the physical properties of the TPU are wellsuited for selective laser sintering processing. The low crystallizationrate of TPU can also make it difficult to maintain tolerances whenlaying down the melt stream onto the parts being built. Further, thebroad melt range for TPU materials can make viscosity control somewhatchallenging and there may be fuming or off gassing issues with usingmany TPU materials.

Given the attractive combination of properties thermoplasticpolyurethanes may offer, and the wide variety of articles made usingmore conventional means of fabrication, there is a growing need toidentify and/or develop thermoplastic polyurethanes well suited forsolid freeform fabrication, and particularly selective laser sintering.

SUMMARY

The disclosed technology provides a system for fabricating athree-dimensional object, comprising a solid freeform fabricationapparatus that selectively fuses layers of powder; wherein said powdercomprises a thermoplastic polyurethane derived from (a) a polyisocyanatecomponent, (b) a polyol component, and (c) an optional chain extendercomponent; wherein said powder has an average particle diameter of lessthan 200 microns (or even less than 150 or less than 100 microns and insome embodiments at least 50 or even 100 microns); wherein the resultingthermoplastic polyurethane has a melting enthalpy (as measured by DSC)of at least 5.5 J/g (or even at least 10 or at least 15 J/g, and in someembodiments less than 100, 50, or even 45 J/g); wherein the resultingthermoplastic polyurethane has a Tc (crystallization temperaturemeasured by DSC) of at least than 70° C., (or even greater than 80° C.or greater than 90° C., and in some embodiments less than 150, 140, oreven less than 130° C.); and wherein the resulting thermoplasticpolyurethane has a Δ(Tm:Tc), (the difference between the Tm and Tc ofthe thermoplastic polyurethane where both are measured by DSC), ofbetween 20 and 75 degrees (or a difference of at least 20, 30, 40, 50,or even 58 degrees and no more than 75, 71, or even 60 degrees).

The disclosed technology provides a method of fabricating athree-dimensional object, comprising the step of: (I) operating a systemfor producing a three-dimensional object from a powder; wherein saidsystem comprises a solid freeform fabrication apparatus that selectivelyfuses layers of powder; so as to form the three-dimensional object;wherein said powder comprises a thermoplastic polyurethane derived from(a) a polyisocyanate component, (b) a polyol component, and (c) anoptional chain extender component; wherein said powder has an averageparticle diameter of less than 200 microns (or even less than 150 orless than 100 microns and in some embodiments at least 50 or even 100microns); wherein the resulting thermoplastic polyurethane has a meltingenthalpy (as measured by DSC) of at least 5.5 J/g (or even at least 10or at least 15 J/g, and in some embodiments less than 100, 50, or even45 J/g); wherein the resulting thermoplastic polyurethane has a Tc(crystallization temperature measured by DSC) of at least than 70° C.,(or even greater than 80° C. or greater than 90° C., and in someembodiments less than 150, 140, or even less than 130° C.); and whereinthe resulting thermoplastic polyurethane has a Δ(Tm:Tc), (the differencebetween the Tm and Tc of the thermoplastic polyurethane where both aremeasured by DSC), of between 20 and 75 degrees (or a difference of atleast 20, 30, 40, 50, or even 58 degrees and no more than 75, 71, oreven 60 degrees).

The disclosed technology provides an article of manufacturing,fabricated by a solid freeform fabrication apparatus that selectivelyfuses layers of powder; wherein said powder has an average particlediameter of less than 200 microns (or even less than 150 or less than100 microns and in some embodiments at least 50 or even 100 microns);wherein the resulting thermoplastic polyurethane has a melting enthalpy(as measured by DSC) of at least 5.5 J/g (or even at least 10 or atleast 15 J/g, and in some embodiments less than 100, 50, or even 45J/g); wherein the resulting thermoplastic polyurethane has a Tc(crystallization temperature measured by DSC) of at least than 70° C.,(or even greater than 80° C. or greater than 90° C., and in someembodiments less than 150, 140, or even less than 130° C.); and whereinthe resulting thermoplastic polyurethane has a Δ(Tm:Tc), (the differencebetween the Tm and Tc of the thermoplastic polyurethane where both aremeasured by DSC), of between 20 and 75 degrees (or a difference of atleast 20, 30, 40, 50, or even 58 degrees and no more than 75, 71, oreven 60 degrees).

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the solid freeform fabricationapparatus comprises: (a) a chamber having a target area at which anadditive process is performed; (b) means for depositing and leveling alayer of powder on said target area; and (c) means for fusing selectedportions of a layer of the powder at said target area.

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein said solid freeform fabricationapparatus comprises a selective laser sintering apparatus.

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the polyisocyanate componentcomprises an aromatic diisocyanate.

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the polyisocyanate componentcomprises 4,4″-methylenebis(phenyl isocyanate).

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the polyol component comprises apolyether polyol, a polyester polyol, a copolymer of polyether andpolyester polyols, or a combination thereof.

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the polyol component comprisespoly(tetramethylene ether glycol), polycaprolactone, a polyesteradipate, a copolymer thereof, or a combination thereof.

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the chain extender componentcomprises a linear alkylene diol.

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the chain extender componentcomprises 1,4-butanediol, 1,12-dodecanediol, dipropylene glycol, or acombination thereof.

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the thermoplastic polyurethanefurther comprises one or more colorants, antioxidants (includingphenolics, phosphites, thioesters, and/or amines), antiozonants,stabilizers, inert fillers, lubricants, inhibitors, hydrolysisstabilizers, light stabilizers, hindered amines light stabilizers,benzotriazole UV absorber, heat stabilizers, stabilizers to preventdiscoloration, dyes, pigments, inorganic and organic fillers,reinforcing agents, or any combinations thereof.

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein said article comprises cook andstorage ware, furniture, automotive components, toys, sportswear,medical devices, personalized medical articles, replicated medicalimplants, dental articles, sterilization containers, drapes, gowns,filters, hygiene products, diapers, films, sheets, tubes, pipes, wirejacketing, cable jacketing, agricultural films, geomembranes, sportingequipment, cast film, blown film, profiles, boat and water craftcomponents, crates, containers, packaging, labware, office floor mats,instrumentation sample holders, liquid storage containers, packagingmaterial, medical tubing and valves, a footwear component, a sheet, atape, a carpet, an adhesive, a wire sheath, a cable, a protectiveapparel, an automotive part, a coating, a foam laminate, an overmoldedarticle, an automotive skin, an awning, a tarp, a leather article, aroofing construction article, a steering wheel, a powder coating, apowder slush molding, a consumer durable, a grip, a handle, a hose, ahose liner, a pipe, a pipe liner, a caster wheel, a skate wheel, acomputer component, a belt, an applique, a footwear component, aconveyor or timing belt, a glove, a fiber, a fabric, or a garment.

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the resulting thermoplasticpolyurethane has a Tm (melting temperature as measured by DSC) of atleast 120° C. (or even greater than 130, 140, 170 or 175° C. and in someembodiments less than 200, 190, or even 180° C.).

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the resulting thermoplasticpolyurethane has a weight average molecular weight, Mw, (measured byGPC) of less than 150,000 (or even less than 140,000, 120,000, or lessthan 100,000, and in some embodiments more than 30,000, 40,00, 50,000,60,000, or even more than 70,000).

The disclosed technology provides any of the systems, methods and/orarticles described herein, wherein the resulting thermoplasticpolyurethane has a Mw/Mn ratio (where Mw is the weight average molecularweight and Mn is the number average molecular weight, where both aremeasured by GPC) of less than 2.7 (or even less than 2.6, less than 2.5,or less than 2.0, and in some embodiments at least 1.0, more than 1.0,more than 1.5, 1.7, or even more than 1.8).

DETAILED DESCRIPTION

Various preferred features and embodiments will be described below byway of non-limiting illustration.

The disclosed technology provides systems for solid freeform fabricationof a three-dimensional objects and/or articles. Also provided aremethods of using such systems and articles made using such systemsand/or methods. The disclosed technology provides these systems,methods, and articles where certain thermoplastic polyurethanes areused, more specifically thermoplastic polyurethanes derived from (a) apolyisocyanate component, (b) a polyol component, and (c) an optionalchain extender component; wherein said powder has an average particlediameter of less than 200 microns (or even less than 150 or less than100 microns and in some embodiments at least 50 or even 100 microns);wherein the resulting thermoplastic polyurethane has a melting enthalpy(as measured by DSC) of at least 5.5 J/g (or even at least 10 or atleast 15 J/g, and in some embodiments less than 100, 50, or even 45J/g); wherein the resulting thermoplastic polyurethane has a Tc(crystallization temperature measured by DSC) of at least than 70° C.,(or even greater than 80° C. or greater than 90° C., and in someembodiments less than 150, 140, or even less than 130° C.); and whereinthe resulting thermoplastic polyurethane has a Δ(Tm:Tc), (the differencebetween the Tm and Tc of the thermoplastic polyurethane where both aremeasured by DSC), of between 20 and 75 degrees (or a difference of atleast 20, 30, 40, 50, or even 58 degrees and no more than 75, 71, oreven 60 degrees). In some of these embodiments, the thermoplasticpolyurethane further has (i) a Tm (melting temperature as measured byDSC) of at least 120° C. (or even greater than 130, 140, 170 or 175° C.and in some embodiments less than 200, 190, or even 180° C.), (ii) aweight average molecular weight, Mw, (measured by GPC) of less than150,000 (or even less than 120,000, or less than 100,000, and in someembodiments more than 30,000, 40,00, 50,000, 60,000, or even more than70,000), and/or (iii) a Mw/Mn ratio (where Mw is the weight averagemolecular weight and Mn is the number average molecular weight, whereboth are measured by GPC) of less than 2.7 (or even less than 2.6, lessthan 2.5, or less than 2.0, and in some embodiments at least 1.0, morethan 1.0, more than 1.5, 1.7, or even more than 1.8).

The Thermoplastic Polyurethanes.

The thermoplastic polyurethanes useful in the described technology arederived from (a) a polyisocyanate component, (b) a polyol component, and(c) an optional chain extender component; wherein the resultingthermoplastic polyurethane meets the parameters described above.

The TPU compositions described herein are made using (a) apolyisocyanate component. The polyisocyanate and/or polyisocyanatecomponent includes one or more polyisocyanates. In some embodiments, thepolyisocyanate component includes one or more diisocyanates.

In some embodiments, the polyisocyanate and/or polyisocyanate componentincludes an alpha, omega-alkylene diisocyanate having from 5 to 20carbon atoms.

Suitable polyisocyanates include aromatic diisocyanates, aliphaticdiisocyanates, or combinations thereof. In some embodiments, thepolyisocyanate component includes one or more aromatic diisocyanates. Insome embodiments, the polyisocyanate component is essentially free of,or even completely free of, aliphatic diisocyanates. In otherembodiments, the polyisocyanate component includes one or more aliphaticdiisocyanates. In some embodiments, the polyisocyanate component isessentially free of, or even completely free of, aromatic diisocyanates.

Examples of useful polyisocyanates include aromatic diisocyanates suchas 4,4′-methylenebis(phenyl isocyanate) (MDI), m-xylene diisocyanate(XDI), phenylene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, andtoluene diisocyanate (TDI); as well as aliphatic diisocyanates such asisophorone diisocyanate 1,4-cyclohexyl diisocyanate (CHDI),decane-1,10-diisocyanate, lysine diisocyanate (LDI), 1,4-butanediisocyanate (BDI), isophorone diisocyanate (PDI),3,3′-dimethyl-4,4′-biphenylene diisocyanate (TODI), 1,5-naphthalenediisocyanate (NDI), and dicyclohexylmethane-4,4″-diisocyanate (H12MDI).Mixtures of two or more polyisocyanates may be used. In someembodiments, the polyisocyanate is MDI and/or H12MDI. In someembodiments, the polyisocyanate includes MDI. In some embodiments, thepolyisocyanate includes H12MDI.

In some embodiments, the thermoplastic polyurethane is prepared with apolyisocyanate component that includes H12MDI. In some embodiments, thethermoplastic polyurethane is prepared with a polyisocyanate componentthat consists essentially of H12MDI. In some embodiments, thethermoplastic polyurethane is prepared with a polyisocyanate componentthat consists of H12MDI.

In some embodiments, the thermoplastic polyurethane is prepared with apolyisocyanate component that includes (or consists essentially of, oreven consists of) H12MDI and at least one of MDI, HDI, TDI, IPDI, LDI,BDI, PDI, CHDI, TODI, and NDI.

In some embodiments, the polyisocyanate used to prepare the TPU and/orTPU compositions described herein is at least 50%, on a weight basis, acycloaliphatic diisocyanate. In some embodiments, the polyisocyanateincludes an alpha, omega-alkylene diisocyanate having from 5 to 20carbon atoms.

In some embodiments, the polyisocyanate used to prepare the TPU and/orTPU compositions described herein includeshexamethylene-1,6-diisocyanate, 1,12-dodecane diisocyanate,2,2,4-trimethyl-hexamethylene diisocyanate,2,4,4-trimethyl-hexamethylene diisocyanate, 2-methyl-1,5-pentamethylenediisocyanate, or combinations thereof.

In some embodiments, the polyisocyanate component comprises an aromaticdiisocyanate. In some embodiments, the polyisocyanate componentcomprises 4,4′-methylenebis(phenyl isocyanate).

The TPU compositions described herein are made using (b) a polyolcomponent. Polyols include polyether polyols, polyester polyols,polycarbonate polyols, polysiloxane polyols, and combinations thereof.

Suitable polyols, which may also be described as hydroxyl terminatedintermediates, when present, may include one or more hydroxyl terminatedpolyesters, one or more hydroxyl terminated polyethers, one or morehydroxyl terminated polycarbonates, one or more hydroxyl terminatedpolysiloxanes, or mixtures thereof.

Suitable hydroxyl terminated polyester intermediates include linearpolyesters having a number average molecular weight (Mn) of from about500 to about 10,000, from about 700 to about 5,000, or from about 700 toabout 4,000, and generally have an acid number less than 1.3 or lessthan 0.5. The molecular weight is determined by assay of the terminalfunctional groups and is related to the number average molecular weight.The polyester intermediates may be produced by (1) an esterificationreaction of one or more glycols with one or more dicarboxylic acids oranhydrides or (2) by transesterification reaction, i.e., the reaction ofone or more glycols with esters of dicarboxylic acids. Mole ratiosgenerally in excess of more than one mole of glycol to acid arepreferred so as to obtain linear chains having a preponderance ofterminal hydroxyl groups. Suitable polyester intermediates also includevarious lactones such as polycaprolactone typically made fromε-caprolactone and a bifunctional initiator such as diethylene glycol.The dicarboxylic acids of the desired polyester can be aliphatic,cycloaliphatic, aromatic, or combinations thereof. Suitable dicarboxylicacids which may be used alone or in mixtures generally have a total offrom 4 to 15 carbon atoms and include: succinic, glutaric, adipic,pimelic, suberic, azelaic, sebacic, dodecanedioic, isophthalic,terephthalic, cyclohexane dicarboxylic, and the like. Anhydrides of theabove dicarboxylic acids such as phthalic anhydride, tetrahydrophthalicanhydride, or the like, can also be used. Adipic acid is a preferredacid. The glycols which are reacted to form a desirable polyesterintermediate can be aliphatic, aromatic, or combinations thereof,including any of the glycols described above in the chain extendersection, and have a total of from 2 to 20 or from 2 to 12 carbon atoms.Suitable examples include ethylene glycol, 1,2-propanediol,1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol,decamethylene glycol, dodecamethylene glycol, and mixtures thereof.

The polyol component may also include one or more polycaprolactonepolyester polyols. The polycaprolactone polyester polyols useful in thetechnology described herein include polyester diols derived fromcaprolactone monomers. The polycaprolactone polyester polyols areterminated by primary hydroxyl groups. Suitable polycaprolactonepolyester polyols may be made from ε-caprolactone and a bifunctionalinitiator such as diethylene glycol, 1,4-butanediol, or any of the otherglycols and/or diols listed herein. In some embodiments, thepolycaprolactone polyester polyols are linear polyester diols derivedfrom caprolactone monomers.

Useful examples include CAPA™ 2202A, a 2000 number average molecularweight (Mn) linear polyester diol, and CAPA™ 2302A, a 3000 Mn linearpolyester diol, both of which are commercially available from PerstorpPolyols Inc. These materials may also be described as polymers of2-oxepanone and 1,4-butanediol.

The polycaprolactone polyester polyols may be prepared from 2-oxepanoneand a diol, where the diol may be 1,4-butanediol, diethylene glycol,monoethylene glycol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, orany combination thereof. In some embodiments, the diol used to preparethe polycaprolactone polyester polyol is linear. In some embodiments,the polycaprolactone polyester polyol is prepared from 1,4-butanediol.In some embodiments, the polycaprolactone polyester polyol has a numberaverage molecular weight from 500 to 10,000, or from 500 to 5,000, orfrom 1,000 or even 2,000 to 4,000 or even 3000.

Suitable hydroxyl terminated polyether intermediates include polyetherpolyols derived from a diol or polyol having a total of from 2 to 15carbon atoms, in some embodiments an alkyl diol or glycol which isreacted with an ether comprising an alkylene oxide having from 2 to 6carbon atoms, typically ethylene oxide or propylene oxide or mixturesthereof. For example, hydroxyl functional polyether can be produced byfirst reacting propylene glycol with propylene oxide followed bysubsequent reaction with ethylene oxide. Primary hydroxyl groupsresulting from ethylene oxide are more reactive than secondary hydroxylgroups and thus are preferred. Useful commercial polyether polyolsinclude poly(ethylene glycol) comprising ethylene oxide reacted withethylene glycol, poly(propylene glycol) comprising propylene oxidereacted with propylene glycol, poly(tetramethylene ether glycol)comprising water reacted with tetrahydrofuran which can also bedescribed as polymerized tetrahydrofuran, and which is commonly referredto as PTMEG. In some embodiments, the polyether intermediate includesPTMEG. Suitable polyether polyols also include polyamide adducts of analkylene oxide and can include, for example, ethylenediamine adductcomprising the reaction product of ethylenediamine and propylene oxide,diethylenetriamine adduct comprising the reaction product ofdiethylenetriamine with propylene oxide, and similar polyamide typepolyether polyols. Copolyethers can also be utilized in the describedcompositions. Typical copolyethers include the reaction product of THFand ethylene oxide or THF and propylene oxide. These are available fromBASF as POLYTHF® B block copolymer and POLYTHF® R random copolymer. Thevarious polyether intermediates generally have a number averagemolecular weight (Mn) as determined by assay of the terminal functionalgroups which is an average molecular weight greater than about 700, suchas from about 700 to about 10,000, from about 1,000 to about 5,000, orfrom about 1,000 to about 2,500. In some embodiments, the polyetherintermediate includes a blend of two or more different molecular weightpolyethers, such as a blend of 2,000 Mn and 1000 Mn PTMEG.

Suitable hydroxyl terminated polycarbonates include those prepared byreacting a glycol with a carbonate. U.S. Pat. No. 4,131,731 is herebyincorporated by reference for its disclosure of hydroxyl terminatedpolycarbonates and their preparation. Such polycarbonates are linear andhave terminal hydroxyl groups with essential exclusion of other terminalgroups. The essential reactants are glycols and carbonates. Suitableglycols are selected from cycloaliphatic and aliphatic diols containing4 to 40, and or even 4 to 12 carbon atoms, and from polyoxyalkyleneglycols containing 2 to 20 alkoxy groups per molecule with each alkoxygroup containing 2 to 4 carbon atoms. Suitable diols include aliphaticdiols containing 4 to 12 carbon atoms such as 1,4-butanediol,1,5-pentanediol, neopentyl glycol, 1,6-hexanediol,2,2,4-trimethyl-1,6-hexanediol, 1,10-decanediol, hydrogenateddilinoleylglycol, hydrogenated dioleylglycol, 3-methyl-1,5-pentanediol;and cycloaliphatic diols such as 1,3-cyclohexanediol,1,4-dimethylolcyclohexane, 1,4-cyclohexanediol-,1,3-dimethylolcyclohexane-, 1,4-endomethylene-2-hydroxy-5-hydroxymethylcyclohexane, and polyalkylene glycols. The diols used in the reactionmay be a single diol or a mixture of diols depending on the propertiesdesired in the finished product. Polycarbonate intermediates which arehydroxyl terminated are generally those known to the art and in theliterature. Suitable carbonates are selected from alkylene carbonatescomposed of a 5 to 7 member ring. Suitable carbonates for use hereininclude ethylene carbonate, trimethylene carbonate, tetramethylenecarbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 2,3-butylenecarbonate, 1,2-ethylene carbonate, 1,3-pentylene carbonate,1,4-pentylene carbonate, 2,3-pentylene carbonate, and 2,4-pentylenecarbonate. Also, suitable herein are dialkylcarbonates, cycloaliphaticcarbonates, and diarylcarbonates. The dialkylcarbonates can contain 2 to5 carbon atoms in each alkyl group and specific examples thereof arediethylcarbonate and dipropylcarbonate. Cycloaliphatic carbonates,especially dicycloaliphatic carbonates, can contain 4 to 7 carbon atomsin each cyclic structure, and there can be one or two of suchstructures. When one group is cycloaliphatic, the other can be eitheralkyl or aryl. On the other hand, if one group is aryl, the other can bealkyl or cycloaliphatic. Examples of suitable diarylcarbonates, whichcan contain 6 to 20 carbon atoms in each aryl group, arediphenylcarbonate, ditolylcarbonate, and dinaphthylcarbonate.

Suitable polysiloxane polyols include alpha-omega-hydroxyl or amine orcarboxylic acid or thiol or epoxy terminated polysiloxanes. Examplesinclude poly(dimethysiloxane) terminated with a hydroxyl or amine orcarboxylic acid or thiol or epoxy group. In some embodiments, thepolysiloxane polyols are hydroxyl terminated polysiloxanes. In someembodiments, the polysiloxane polyols have a number-average molecularweight in the range from 300 to 5,000, or from 400 to 3,000.

Polysiloxane polyols may be obtained by the dehydrogenation reactionbetween a polysiloxane hydride and an aliphatic polyhydric alcohol orpolyoxyalkylene alcohol to introduce the alcoholic hydroxy groups ontothe polysiloxane backbone.

In some embodiments, the polysiloxanes may be represented by one or morecompounds having the following formula:

in which: each R¹ and R² are independently a 1 to 4 carbon atom alkylgroup, a benzyl, or a phenyl group; each E is OH or NHR³ where R³ ishydrogen, a 1 to 6 carbon atoms alkyl group, or a 5 to 8 carbon atomscyclo-alkyl group; a and b are each independently an integer from 2 to8; c is an integer from 3 to 50. In amino-containing polysiloxanes, atleast one of the E groups is NHR³. In the hydroxyl-containingpolysiloxanes, at least one of the E groups is OH. In some embodiments,both R¹ and R² are methyl groups.

Suitable examples include alpha-omega-hydroxypropyl terminatedpoly(dimethysiloxane) and alpha-omega-amino propyl terminatedpoly(dimethysiloxane), both of which are commercially availablematerials. Further examples include copolymers of thepoly(dimethysiloxane) materials with a poly(alkylene oxide).

The polyol component, when present, may include poly(ethylene glycol),poly(tetramethylene ether glycol), poly(trimethylene oxide), ethyleneoxide capped poly(propylene glycol), poly(butylene adipate),poly(ethylene adipate), poly(hexamethylene adipate),poly(tetramethylene-co-hexamethylene adipate),poly(3-methyl-1,5-pentamethylene adipate), polycaprolactone diol,poly(hexamethylene carbonate) glycol, poly(pentamethylene carbonate)glycol, poly(trimethylene carbonate) glycol, dimer fatty acid basedpolyester polyols, vegetable oil based polyols, or any combinationthereof.

Examples of dimer fatty acids that may be used to prepare suitablepolyester polyols include PRIPLAST™ polyester glycols/polyolscommercially available from Croda and RADIA® polyester glycolscommercially available from Oleon.

In some embodiments, the polyol component includes a polyether polyol, apolycarbonate polyol, a polycaprolactone polyol, or any combinationthereof.

In some embodiments, the polyol component includes a polyether polyol.In some embodiments, the polyol component is essentially free of or evencompletely free of polyester polyols. In some embodiments, the polyolcomponent used to prepare the TPU is substantially free of, or evencompletely free of polysiloxanes.

In some embodiments, the polyol component includes ethylene oxide,propylene oxide, butylene oxide, styrene oxide, poly(tetramethyleneether glycol), poly(propylene glycol), poly(ethylene glycol), copolymersof poly(ethylene glycol) and poly(propylene glycol), epichlorohydrin,and the like, or combinations thereof. In some embodiments, the polyolcomponent includes poly(tetramethylene ether glycol).

In some embodiments the polyol has a number average molecular weight ofat least 900. In other embodiments the polyol has a number averagemolecular weight of at least 900, 1,000, 1,500, 1,750, and/or a numberaverage molecular weight up to 5,000, 4,000, 3,000, 2,500, or even2,000.

In some embodiments, the polyol component comprises a polycaprolactonepolyester polyether polyol, a polyether polyol, a polycaprolactonepolyester polyether copolymer polyol, a polyester polyol, or anycombination thereof.

In some embodiments, the polyol component comprises a polycaprolactonepolyester polyether polyol, a poly(tetramethylene ether glycol), apolycaprolactone polyester poly(tetramethylene ether glycol) copolymerpolyol, a polybutylene adipate, a polybutylene-hexylene adipate (anadipate made from a mixture of 1,4-butanediol and 1,6-hexanediol), orany combination thereof. In some embodiments, the polyol componentcomprises a polycaprolactone polyester poly(tetramethylene ether glycol)copolymer polyol.

The TPU compositions described herein are made using c) a chain extendercomponent. Chain extenders include diols, diamines, and combinationthereof.

Suitable chain extenders include relatively small polyhydroxy compounds,for example lower aliphatic or short chain glycols having from 2 to 20,or 2 to 12, or 2 to 10 carbon atoms. Suitable examples include ethyleneglycol, diethylene glycol, propylene glycol, dipropylene glycol,1,4-butanediol (BDO), 1,6-hexanediol (HDO), 1,3-butanediol,1,5-pentanediol, neopentylglycol, 1,4-cyclohexanedimethanol (CHDM),2,2-bis[4-(2-hydroxyethoxy) phenyl]propane (HEPP), hexamethylenediol,heptanediol, nonanediol, dodecanediol, 3-methyl-1,5-pentanediol,ethylenediamine, butanediamine, hexamethylenediamine, and hydroxyethylresorcinol (HER), and the like, as well as mixtures thereof. In someembodiments, the chain extender includes BDO, HDO,3-methyl-1,5-pentanediol, or a combination thereof. In some embodiments,the chain extender includes BDO. Other glycols, such as aromatic glycolscould be used, but in some embodiments the TPUs described herein areessentially free of or even completely free of such materials.

In some embodiments, the chain extender used to prepare the TPU issubstantially free of, or even completely free of, 1,6-hexanediol. Insome embodiments, the chain extender used to prepare the TPU includes acyclic chain extender. Suitable examples include CHDM, HEPP, HER, andcombinations thereof. In some embodiments, the chain extender used toprepare the TPU includes an aromatic cyclic chain extender, for example,HEPP, HER, or a combination thereof. In some embodiments, the chainextender used to prepare the TPU includes an aliphatic cyclic chainextender, for example, CHDM. In some embodiments, the chain extenderused to prepare the TPU is substantially free of, or even completelyfree of aromatic chain extenders, for example, aromatic cyclic chainextenders. In some embodiments, the chain extender used to prepare theTPU is substantially free of, or even completely free of polysiloxanes.

In some embodiments, the chain extender component includes1,4-butanediol, 2-ethyl-1,3-hexanediol, 2,2,4-trimethylpentane-1,3-diol, 1,6-hexanediol, 1,4-cyclohexane dimethylol,1,3-propanediol, 3-methyl-1,5-pentanediol or combinations thereof. Insome embodiments, the chain extender component includes 1,4-butanediol,3-methyl-1,5-pentanediol or combinations thereof. In some embodiments,the chain extender component includes 1,4-butanediol.

In some embodiments, the chain extender component comprises a linearalkylene diol. In some embodiments, the chain extender componentcomprises 1,4-butanediol, dipropylene glycol, or a combination of thetwo. In some embodiments, the chain extender component comprises1,4-butanediol.

In some embodiments, the mole ratio of the chain extender to the polyolis greater than 1.5. In other embodiments, the mole ratio of the chainextender to the polyol is at least (or greater than) 1.5, 2.0, 3.5, 3.7,or even 3.8 and/or the mole ratio of the chain extender to the polyolmay go up to 5.0, or even 4.0.

The thermoplastic polyurethanes described herein may also be consideredto be thermoplastic polyurethane (TPU) compositions. In suchembodiments, the compositions may contain one or more TPU. These TPU areprepared by reacting: a) the polyisocyanate component described above;b) the polyol component described above; and c) the chain extendercomponent described above, where the reaction may be carried out in thepresence of a catalyst. At least one of the TPU in the composition mustmeet the parameters described above making it suitable for solidfreeform fabrication, and in particular fused deposition modeling.

The means by which the reaction is carried out is not overly limited,and includes both batch and continuous processing. In some embodiments,the technology deals with batch processing of aliphatic TPU. In someembodiments, the technology deals with continuous processing ofaliphatic TPU.

The described compositions include the TPU materials described above andalso TPU compositions that include such TPU materials and one or moreadditional components. These additional components include otherpolymeric materials that may be blended with the TPU described herein.These additional components include one or more additives that may beadded to the TPU, or blend containing the TPU, to impact the propertiesof the composition.

The TPU described herein may also be blended with one or more otherpolymers. The polymers with which the TPU described herein may beblended are not overly limited. In some embodiments, the describedcompositions include two or more of the described TPU materials. In someembodiments, the compositions include at least one of the described TPUmaterials and at least one other polymer, which is not one of thedescribed TPU materials.

Polymers that may be used in combination with the TPU materialsdescribed herein also include more conventional TPU materials such asnon-caprolactone polyester-based TPU, polyether-based TPU, or TPUcontaining both non-caprolactone polyester and polyether groups. Othersuitable materials that may be blended with the TPU materials describedherein include polycarbonates, polyolefins, styrenic polymers, acrylicpolymers, polyoxymethylene polymers, polyamides, polyphenylene oxides,polyphenylene sulfides, polyvinylchlorides, chlorinated polyvinylchlorides, polylactic acids, or combinations thereof.

Polymers for use in the blends described herein include homopolymers andcopolymers. Suitable examples include: (i) a polyolefin (PO), such aspolyethylene (PE), polypropylene (PP), polybutene, ethylene propylenerubber (EPR), polyoxyethylene (POE), cyclic olefin copolymer (COC), orcombinations thereof; (ii) a styrenic, such as polystyrene (PS),acrylonitrile butadiene styrene (ABS), styrene acrylonitrile (SAN),styrene butadiene rubber (SBR or HIPS), polyalphamethylstyrene, styrenemaleic anhydride (SMA), styrene-butadiene copolymer (SBC) (such asstyrene-butadiene-styrene copolymer (SBS) andstyrene-ethylene/butadiene-styrene copolymer (SEBS)),styrene-ethylene/propylene-styrene copolymer (SEPS), styrene butadienelatex (SBL), SAN modified with ethylene propylene diene monomer (EPDM)and/or acrylic elastomers (for example, PS-SBR copolymers), orcombinations thereof; (iii) a thermoplastic polyurethane (TPU) otherthan those described above; (iv) a polyamide, such as Nylon™, includingpolyamide 6,6 (PA66), polyamide 1,1 (PA11), polyamide 1,2 (PA12), acopolyamide (COPA), or combinations thereof; (v) an acrylic polymer,such as polymethyl acrylate, polymethylmethacrylate, a methylmethacrylate styrene (MS) copolymer, or combinations thereof; (vi) apolyvinylchloride (PVC), a chlorinated polyvinylchloride (CPVC), orcombinations thereof; (vii) a polyoxyemethylene, such as polyacetal;(viii) a polyester, such as polyethylene terephthalate (PET),polybutylene terephthalate (PBT), copolyesters and/or polyesterelastomers (COPE) including polyether-ester block copolymers such asglycol modified polyethylene terephthalate (PETG), polylactic acid(PLA), polyglycolic acid (PGA), copolymers of PLA and PGA, orcombinations thereof; (ix) a polycarbonate (PC), a polyphenylene sulfide(PPS), a polyphenylene oxide (PPO), or combinations thereof; orcombinations thereof.

In some embodiments, these blends include one or more additionalpolymeric materials selected from groups (i), (iii), (vii), (viii), orsome combination thereof. In some embodiments, these blends include oneor more additional polymeric materials selected from group (i). In someembodiments, these blends include one or more additional polymericmaterials selected from group (iii). In some embodiments, these blendsinclude one or more additional polymeric materials selected from group(vii). In some embodiments, these blends include one or more additionalpolymeric materials selected from group (viii).

The additional additives suitable for use in the TPU compositionsdescribed herein are not overly limited. Suitable additives includepigments, UV stabilizers, UV absorbers, antioxidants, lubricity agents,heat stabilizers, hydrolysis stabilizers, cross-linking activators,flame retardants, layered silicates, fillers, colorants, reinforcingagents, adhesion mediators, impact strength modifiers, antimicrobials,and any combination thereof.

In some embodiments, the additional component is a flame retardant.Suitable flame retardants are not overly limited and may include a boronphosphate flame retardant, a magnesium oxide, a dipentaerythritol, apolytetrafluoroethylene (PTFE) polymer, or any combination thereof. Insome embodiments, this flame retardant may include a boron phosphateflame retardant, a magnesium oxide, a dipentaerythritol, or anycombination thereof. A suitable example of a boron phosphate flameretardant is BUDIT 326, commercially available from Budenheim USA, Inc.When present, the flame retardant component may be present in an amountfrom 0 to 10 weight percent of the overall TPU composition, in otherembodiments from 0.5 to 10, or from 1 to 10, or from 0.5 or 1 to 5, orfrom 0.5 to 3, or even from 1 to 3 weight percent of the overall TPUcomposition.

The TPU compositions described herein may also include additionaladditives, which may be referred to as a stabilizer. The stabilizers mayinclude antioxidants such as phenolics, phosphites, thioesters, andamines, light stabilizers such as hindered amine light stabilizers andbenzothiazole UV absorbers, and other process stabilizers andcombinations thereof. In one embodiment, the preferred stabilizer isIrganox 1010 from BASF and Naugard 445 from Chemtura. The stabilizer isused in the amount from about 0.1 weight percent to about 5 weightpercent, in another embodiment from about 0.1 weight percent to about 3weight percent, and in another embodiment from about 0.5 weight percentto about 1.5 weight percent of the TPU composition.

In addition, various conventional inorganic flame retardant componentsmay be employed in the TPU composition. Suitable inorganic flameretardants include any of those known to one skilled in the art, such asmetal oxides, metal oxide hydrates, metal carbonates, ammoniumphosphate, ammonium polyphosphate, calcium carbonate, antimony oxide,clay, mineral clays including talc, kaolin, wollastonite, nanoclay,montmorillonite clay which is often referred to as nano-clay, andmixtures thereof. In one embodiment, the flame retardant packageincludes talc. The talc in the flame retardant package promotesproperties of high limiting oxygen index (LOI). The inorganic flameretardants may be used in the amount from 0 to about 30 weight percent,from about 0.1 weight percent to about 20 weight percent, in anotherembodiment about 0.5 weight percent to about 15 weight percent of thetotal weight of the TPU composition.

Still further optional additives may be used in the TPU compositionsdescribed herein. The additives include colorants, antioxidants(including phenolics, phosphites, thioesters, and/or amines),antiozonants, stabilizers, inert fillers, lubricants, inhibitors,hydrolysis stabilizers, light stabilizers, hindered amines lightstabilizers, benzotriazole UV absorber, heat stabilizers, stabilizers toprevent discoloration, dyes, pigments, inorganic and organic fillers,reinforcing agents and combinations thereof.

All of the additives described above may be used in an effective amountcustomary for these substances. The non-flame retardants additives maybe used in amounts of from about 0 to about 30 weight percent, in oneembodiment from about 0.1 to about 25 weight percent, and in anotherembodiment about 0.1 to about 20 weight percent of the total weight ofthe TPU composition.

These additional additives can be incorporated into the components of,or into the reaction mixture for, the preparation of the TPU resin, orafter making the TPU resin. In another process, all the materials can bemixed with the TPU resin and then melted or they can be incorporateddirectly into the melt of the TPU resin.

The TPU materials described above may be prepared by a process thatincludes the step of (I) reacting: a) the polyisocyanate componentdescribed above; b) the polyol component described above; and c) thechain extender component described above, where the reaction may becarried out in the presence of a catalyst, resulting in a thermoplasticpolyurethane composition.

The process may further include the step of: (II) mixing the TPUcomposition of step (I) with one or more blend components, including oneor more additional TPU materials and/or polymers, including any of thosedescribed above.

The process may further include the step of: (II) mixing the TPUcomposition of step (I) with one or more of the additional additivesdescribed above.

The process may further include the step of: (II) mixing the TPUcomposition of step (I) with one or more blend components, including oneor more additional TPU materials and/or polymers, including any of thosedescribed above, and/or the step of: (III) mixing the TPU composition ofstep (I) with one or more of the additional additives described above.

While not wishing to be bound by theory it is believed that any TPU thatmeets the requirements described herein will be better suited forfreeform fabrication, in particular the selective laser sintering, thanany TPU that do not. While not wishing to be bound by theory, thenecessary parameters are believed to be (i) a melting enthalpy (asmeasured by DSC) is at least 5.5 J/g (or even at least 10 or at least 15J/g, and in some embodiments less than 100, 50, 40, or even 20 J/ghowever it is noted that while not wishing to be bound by theory ahigher melting enthalpy is considered to be better for this applicationand that there may be no real maximum limit for the melting enthalpy butin the event that one would want to limit the melting enthalpy due topractical consideration and/or the properties of readily availablematerials, the maximum limits provided above could be used in someembodiments); (ii) a Tc (crystallization temperature measured by DSC) ofat least than 70° C., (or even greater than 80° C. or greater than 90°C., and in some embodiments less than 150, 140, or even 130° C.); and(iii) a Δ(Tm:Tc), (the difference between the Tm and Tc of the TPU whereboth are measured by DSC), of between 20 and 75 (or a difference of atleast 20, 30, 40, 50, or even 58 degrees and no more than 75, 71, oreven 60 degrees). The physical properties of the power of the TPU arealso important and it is believed that the powder should have an averageparticle diameter of less than 200 microns (or even less than 150 orless than 100 microns). The combination of these parameters is believedto provide TPU well suited for freeform fabrication, in particularselective laser sintering.

In addition, in at least some embodiments, the following parameters arealso believed to be important: the resulting thermoplastic polyurethanehas (i) a Tm (melting temperature as measured by DSC) of at least 120°C. (or even greater than 130, 140, 170 or 175° C. and in someembodiments less than 200, 190, or even 180° C.), (ii) a weight averagemolecular weight, Mw, (measured by GPC) of less than 150,000 (or evenless than 120,000, or less than 100,000, and in some embodiments morethan 30,000, 40,00, 50,000, 60,000, or even more than 70,000), and/or(iii) a Mw/Mn ratio (where Mw is the weight average molecular weight andMn is the number average molecular weight, where both are measured byGPC) of less than 2.7 (or even less than 2.6, less than 2.5, or lessthan 2.0, and in some embodiments at least 1.0, more than 1.0, more than1.5, 1.7, or even more than 1.8).

The Systems and Methods

The solid freeform fabrication systems, in particular the selectivelaser sintering systems and the methods of using the same useful in thedescribed technology are not overly limited. It is noted that thedescribed technology provides certain thermoplastic polyurethanes thatare better suited for solid freeform fabrication systems, in particularselective laser sintering systems, than other thermoplasticpolyurethanes, and the key to the described technology is that relativebenefit. It is noted that some solid freeform fabrication systems,including some selective laser sintering systems may be better suitedfor processing certain materials, including thermoplastic polyurethanes,due to their equipment configurations, processing parameters, etc.However, the described technology is not focused on the details of solidfreeform fabrication systems, including some selective laser sinteringsystems, rather the described technology is focused on providing certainthermoplastic polyurethanes that are better suited for solid freeformfabrication systems generally, in particular selective laser sinteringsystems generally.

Selective laser sintering is an example of a freeform fabricationtechnology and includes processes practiced in systems available from 3DSystems, Inc., in which articles are produced from a laser-fusiblepowder in layerwise fashion. In some embodiments selective lasersintering involves using a thin layer of powder which is dispensed andthen fused, melted, or sintered, by laser energy that is directed tothose portions of the powder corresponding to a cross-section of thearticle. Conventional selective laser sintering systems, such as theVANGUARD™ system available from 3D Systems, Inc., position the laserbeam by way of galvanometer-driven mirrors that deflect the laser beam.The deflection of the laser beam is controlled, in combination withmodulation of the laser itself, to direct laser energy to thoselocations of the fusible powder layer corresponding to the cross-sectionof the article to be formed in that layer. The computer based controlsystem can be programmed with information indicative of the desiredboundaries of a plurality of cross sections of the part to be produced.The laser may be scanned across the powder in raster fashion, withmodulation of the laser affected in combination therewith, or the lasermay be directed in vector fashion. In some applications, cross-sectionsof articles are formed in a powder layer by fusing powder along theoutline of the cross-section in vector fashion either before or after araster scan that “fills” the area within the vector-drawn outline. Inany case, after the selective fusing of powder in a given layer, anadditional layer of powder is then dispensed, and the process repeated,with fused portions of later layers fusing to fused portions of previouslayers (as appropriate for the article), until the article is complete.

Detailed description of the selective laser sintering technology may befound in U.S. Pat. Nos. 4,863,538, 5,132,143 and 4,944,817, all assignedto Board of Regents, The University of Texas System, and in U.S. Pat.No. 4,247,508, Housholder, all incorporated herein by this reference.

Selective laser sintering technology has enabled the direct manufactureof three-dimensional articles of high resolution and dimensionalaccuracy from a variety of materials including polystyrene, some nylons,other plastics, and composite materials such as polymer coated metalsand ceramics. Polystyrene parts may be used in the generation of toolingby way of the well-known “lost wax” process. In addition, selectivelaser sintering may be used for the direct fabrication of molds from aCAD database representation of the object to be molded in the fabricatedmolds; in this case, computer operations will “invert” the CAD databaserepresentation of the object to be formed, to directly form the negativemolds from the powder. Using the disclose technology the described TPUmaterials may now be successively used in selective laser sinteringtechnology as well.

In some embodiments, laser sintering systems utilize dual pistoncartridge feed systems with a counter-rotating roller and an infraredsensor or pyrometer to measure the thermal conditions in the processchamber and the powder bed.

In some embodiments, the thermoplastic polyurethanes used in thedescribed technology are in the form of a powder having the followingcharacteristics: a d50 particle size distribution of between 20 and 100microns, preferably between 30 and 70 microns, and also satisfying thefollowing equation: (d90-d10)/d50 between 0.85 and 1.2; a sphericityfactor of between 0.8 and 1, preferably between 0.85 and 1; and anintraparticle porosity lower than 0.05 ml/g, preferably lower than 0.02ml/g. As used herein, powder means an assembly of powder particles.

The particle size distribution of the objects may be obtained by laserdiffraction measurement on a Malvern granulometer, using a wet module.The quantities used in this document concern d10, d50 and d90. The d10mesh is the dimension such that 10% of the particles are smaller thanthis dimension and 90% of the particles are larger than this dimension.The d50 mesh is the dimension such that 50% of the particles are smallerthan this dimension and 50% of the particles are larger than thisdimension. The d90 mesh is the dimension such that 90% of the particlesare smaller than this dimension and 10% of the particles are larger thanthis dimension.

The sphericity factor may be measured as follows: To quantify thesphericity of the objects, use is made of image analysis in thefollowing manner. The characteristic wavelengths of the small and largediameters for each object are measured on at least 100 objects. For eachobject, the sphericity factor is defined as the ratio of the smalldiameter to the large diameter. For a perfect sphere, the ratio is 1.For grains of variable morphology, this ratio is lower than and tendstoward 1 when approaching perfect sphericity. On 100 objects sampled,the sphericity factor is calculated from the ratio of the diameters, andthe mean sphericity factor is then calculated. To do this, in a mannerknown per se, the sample of particles is dispersed on a glass slideplaced under an optical microscope and the characteristic lengths arerecorded in succession.

The intraparticle porosity may be measured as follows: The poroustexture of the objects is determined by mercury porosimetry using anAUTOPORE IV™ instrument from Micromeritics. This method is based on theintrusion of mercury into the intergranular and intragranular porenetwork. This intrusion is managed via a pressure increase. The powderof the invention may have an intraparticle porosity lower than 0.05ml/g, for pore sizes between 0.01 and 1 microns.

The flowability of the powders may be measured by shearing a sample bythe ring shear tester (sold by D. Schulze, Germany). The powders can bepre-sheared on a cell having an area of 81 cm² with a normal stressequivalent to a mass of 4.3 kg. Powder flowability is a technicalconcept which is also well known to a person skilled in the art; forfurther details, reference can be made in particular to the work:“Standard shear testing technique for particulate solids using theJenike shear cell”, published by “The institution of ChemicalEngineers”, 1989 (ISBN: 0852952325).

The packed density may be measured as follows: powder is poured into a250 ml glass graduated cylinder, previously weighed. The top of thecylinder is leveled. The weighed cylinder is placed on the volumenometerand the level of the powder bed is read on the graduation of thecylinder after 2048 strokes. The test conforms to the one reported inthe text of the European pharmacopoeia, 1997.

The powder of the invention can be obtained in various ways known to aperson skilled in the art, according to the materials used. Mention canbe made in particular, for example, of the documents EP1797141 andWO2007/115977.

In some embodiments, the materials used in the disclose technology arefree of polyamides and related materials, including but not limited tonylon 6, nylon 6-6, nylon 11, nylon 12, nylons 4-6, 6-10, 6-12, 12-12,6-36; semi-aromatic polyamides, for example, polyphthalamides obtainedfrom terephthalic and/or isophthalic acid, such as the polyamide sold bythe trade name AMODEL, and copolymers and alloys thereof.

In some embodiments, the powder may have (i) an intraparticle porositylower than 0.05 ml/g, or lower than 0.02 ml/g, in particular for poresizes of 0.01 .mu.m or higher; (ii) a sphericity factor of between 0.8and 1, 0.85 and 1, or even between 0.9 and 1; (iii) a flowability ofbetween 30 and 60; and/or (iv) an apparent density of between 500 and700 g/l and a packed density of between 550 and 800 g/l.

Production by selective fusion of layers is a method for producingarticles that consists in depositing layers of materials in powder form,selectively melting a portion or a region of a layer, depositing a newlayer of powder and again melting a portion of said layer, andcontinuing in this manner until the desired object is obtained. Theselectivity of the portion of the layer to be melted is obtained forexample, by using absorbers, inhibitors, masks, or via the input offocused energy, such as a laser or electromagnetic beam, for example.Sintering by the addition of layers is preferred, in particular rapidprototyping by sintering using a laser. Rapid prototyping is a methodused to obtain parts of complex shape without tools and withoutmachining, from a three-dimensional image of the article to be produced,by sintering superimposed powder layers using a laser. Generalinformation about rapid prototyping by laser sintering is provided inU.S. Pat. No. 6,136,948 and applications WO96/06881 and US20040138363.

Machines for implementing these methods may comprise a constructionchamber on a production piston, surrounded on the left and right by twopistons feeding the powder, a laser, and means for spreading the powder,such as a roller. The chamber is generally maintained at constanttemperature to avoid deformations.

Other production methods by layer additions' such as those described inWO 01/38061 and EP1015214 are also suitable. These two methods useinfrared heating to melt the powder. The selectivity of the molten partsis obtained in the case of the first method by the use of inhibitors,and in the case of the second method by the use of a mask. Anothermethod is described in application DE10311438. In this method, theenergy for melting the polymer is supplied by a microwave generator andselectivity is obtained by using a susceptor. The disclosed technologyfurther provides the use of the described thermoplastic polyurethanes inthe described systems and methods, and the articles made from the same.

The Articles

The systems and methods described herein may utilize the thermoplasticpolyurethanes described herein and produce various objects and/orarticles. Objects and/or articles made with the disclosed technology arenot overly limited.

In some embodiments, the object and/or article comprises cook andstorage ware, furniture, automotive components, toys, sportswear,medical devices, personalized medical articles, replicated medicalimplants, dental articles, sterilization containers, drapes, gowns,filters, hygiene products, diapers, films, sheets, tubes, pipes, wirejacketing, cable jacketing, agricultural films, geomembranes, sportingequipment, cast film, blown film, profiles, boat and water craftcomponents, crates, containers, packaging, labware, office floor mats,instrumentation sample holders, liquid storage containers, packagingmaterial, medical tubing and valves, a footwear component, a sheet, atape, a carpet, an adhesive, a wire sheath, a cable, a protectiveapparel, an automotive part, a coating, a foam laminate, an overmoldedarticle, an automotive skin, an awning, a tarp, a leather article, aroofing construction article, a steering wheel, a powder coating, apowder slush molding, a consumer durable, a grip, a handle, a hose, ahose liner, a pipe, a pipe liner, a caster wheel, a skate wheel, acomputer component, a belt, an applique, a footwear component, aconveyor or timing belt, a glove, a fiber, a fabric, or a garment.

Additional articles that may be used in the present invention includes,jewelry, customized keepsakes and/or collectibles, such as but notlimited to coins medallions, frames and picture frames, eyewear frames,keys, cups, mugs, miniatures and models, wrist bands, personalizedaction figures, and the like.

As with all additive manufacturing there is particular value for suchtechnology in making articles as part of rapid prototyping and newproduct development, as part of making custom and/or one time onlyparts, or similar applications where mass production of an article inlarge numbers is not warranted and/or practical.

More generally, the compositions of the invention, including any blendsthereof, may be useful in a wide variety of applications, includingtransparent articles such as cook and storage ware, and in otherarticles such as automotive components, sterilizable medical devices,fibers, woven fabrics, nonwoven fabrics, oriented films, and other sucharticles. The compositions are suitable for automotive components suchas bumpers, grills, trim parts, dashboards and instrument panels,exterior door and hood components, spoiler, wind screen, hub caps,mirror housing, body panel, protective side molding, and other interiorand external components associated with automobiles, trucks, boats, andother vehicles.

Other useful articles and goods may be formed from the compositions ofthe invention including: labware, such as roller bottles for culturegrowth and media bottles, instrumentation sample windows; liquid storagecontainers such as bags, pouches, and bottles for storage and IVinfusion of blood or solutions; packaging material including those forany medical device or drugs including unit-dose or other blister orbubble pack as well as for wrapping or containing food preserved byirradiation. Other useful items include medical tubing and valves forany medical device including infusion kits, catheters, and respiratorytherapy, as well as packaging materials for medical devices or foodwhich is irradiated including trays, as well as stored liquid,particularly water, milk, or juice, containers including unit servingsand bulk storage containers as well as transfer means such as tubing,hoses, pipes, and such, including liners and/or jackets thereof. In someembodiments, the articles of the invention are fire hoses that include aliner made from the TPU compositions described herein. In someembodiments the, liner is a layer applied to the inner jacket of thefire hose.

Still further useful applications and articles include: automotivearticle including air bag covers, interior surfaces of automobiles;biomedical devices including implantable devices, pacemaker leads,artificial hearts, heart valves, stent coverings, artificial tendons,arteries and veins, implants containing pharmaceutically active agents,medical bags, medical tubing, drug delivery devices such as intravaginalrings, and bioabsorbable implants; shoe related articles including anupper and a sole, where the sole may include an insole, a midsole, andan outsole, adhesive systems to connect any of the parts described,other footwear parts including adhesives and fabric coatings, cleats,membranes, gas bladders, gel bladders or fluid bladders, inflated orinflatable inserts, laminated inserts, cushioning devices, soles madewith microspheres, heels, wheels embedded in the shoe sole, inflatabletongues, woven and unwoven fabric, odor and moisture absorbent pads,pressurized ankle collars, eyelets and laces, orthotic device or insert,gel pads, resilient pads, barrier membranes and fabrics, and artificialleather; golf ball related articles including 2 piece and 3 piece golfballs, including the cover and the core.

Of particular relevance are personalized medical articles, such asorthotics, implants, bones, dental items, veins, etc that are customizedto the patient. For example, bone sections and/or implants may beprepared using the systems and methods described above, for a specificpatient where the implants are designed specifically for the patient.

The amount of each chemical component described is presented exclusiveof any solvent or diluent oil, which may be customarily present in thecommercial material, that is, on an active chemical basis, unlessotherwise indicated. However, unless otherwise indicated, each chemicalor composition referred to herein should be interpreted as being acommercial grade material which may contain the isomers, by-products,derivatives, and other such materials which are normally understood tobe present in the commercial grade.

It is known that some of the materials described above may interact inthe final formulation, so that the components of the final formulationmay be different from those that are initially added. For instance,metal ions (of, e.g., a flame retardant) can migrate to other acidic oranionic sites of other molecules. The products formed thereby, includingthe products formed upon employing the composition of the technologydescribed herein in its intended use, may not be susceptible of easydescription. Nevertheless, all such modifications and reaction productsare included within the scope of the technology described herein; thetechnology described herein encompasses the composition prepared byadmixing the components described above.

EXAMPLES

The technology described herein may be better understood with referenceto the following non-limiting examples.

Materials. Several thermoplastic polyurethanes (TPU) as well as severalother non-TPU reference materials are evaluated for their suitability ofuse in selective laser sintering.

Example A is 95A polyether copolymer TPU.

Example B is 94A polyether TPU.

Example C is 91A polyester TPU.

Example D is 52D polyester TPU.

Example E is 90A polycaprolactone TPU.

Example F is 88A aliphatic polyether TPU.

Example G is 94A polyester TPU.

Example H is 90A polyether TPU.

Example I is 93A polycaprolactone copolyester TPU.

Example J is 90A polyether TPU.

Example K is 95A polycaprolactone TPU.

Examples A, B, and C are considered to be inventive examples. ExamplesD, E, F, G, H, I, J, and K are considered to be comparative TPUexamples, where each material fails to meet at least one parameterconsidered to be needed in order for the TPU to be well suited forselective laser sintering. Each TPU material is tested to determine itssuitability for use in selective laser sintering (SLS) processes. Theresults of this testing are summarized below. All melting temperatures,temperatures of crystallization, and melting enthalpies are measured byDSC. All molecular weight values are measured by GPC.

TABLE 1 Summary of TPU Properties related to SLS processing Tm TcΔ(Tm:Tc) ΔHm (° C.) (° C.) (° C.) (J/g) Mw Mn Mw/Mn Ex A 179 120 59 15.496,902 53,243 1.82 Ex B 142 83 59 37.8 109,760 50,119 2.19 Ex C 174 9975 5.7 135,700 51,208 2.65 Ex D 60 40 20 90.4 119,631 53,407 2.24 Ex E119 54 65 27 321,241 142,142 2.26 Ex F 105 47 58 20.5 158,127 58,566 2.7Ex G 155 72 83 7.8 625,21 31,105 2.01 Ex H 188 115 73 5.1 110,500 51,8782.13 Ex I 177 114 63 4.3 132,747 62,031 2.14 Ex J 179 88 91 14.4 203,70087,425 2.33 Ex K 164 85 79 12.3 289,800 89,444 3.24

Based on these results, TPU Examples A, B, and C are suitable TPU forlaser sintering processing and would be expected to process well. Thesematerials were further tested in a selective laser sintering process toverify the specified parameters are necessary for TPU materials to besuitable for, and more likely to process well in, selective lasersintering processes.

The selected materials are tested on a 3D Systems SINTERSTATIONVANGUARD™ machine with the HiQ upgrade. All tests are conducted in anitrogen atmosphere. Since a commercial material profile must be enteredto set the machine parameter defaults, the library values for Duraform(nylon) EX were selected. Changes from this default setting are notedbelow. Each example is tested in the form of a powder. Generally, thepowder was either coarse, granular and/or sandy, or in contrast fine,clumpy, and/or floury and samples were sifted prior to testing. It isnoted below where the properties of powder are believed to have animpact on the processing.

Example A

For Example A the powder tested was fine and clumpy. The powder wassieved in the 70 mesh sieve. It was loaded into the chamber and all binswere heated to 110° C. The powder spread well, so the part bintemperature was increased to 150° C. and then 160° C. Powder spreadingwas still acceptable. The part bin/feed bin temperatures were increasedto the following values while assuring that the powder continued tospread well: 170° C./120° C., then 175° C./130° C., and then 178°C./140° C. The maximum temperature for the feed bins is 140° C. As thereported melt point was 179° C. (Table 1), the temperature was notincreased further. The powder was still spreading reasonably well, butsome clumping appeared at this high temperature. The six tension couponrun was begun with three pairs of samples at 35, 45 and 55 watts power.Initially, the part layer thickness was 0.005 in, and the feed layerthickness was 0.020 in. As the run progressed, the powder was behavingwell, so the part layer thickness was decreased to 0.004 in, and thefeed layer thickness was eventually set at 0.018 in. The part builtsuccessfully, although some powder clumping was observed duringspreading. Approximately 0.1 in of powder was fed to the part bin, and asecond set of tension coupons was built. Since the powder seemed to berunning well overall, three random small parts were added to the tensioncoupon build. There was some undesirable clumping observed, so the partbin temperature was lowered to 170° C., and the feed bin temperature waslowered to 135° C. After 4-5 layers, powder clumping was still occurringto some degree, so the feed bin temperature was lowered to 125° C. Aftera few layers, the part bin and feed bin temperatures were reduced to160° C. and 120° C., respectively. This corrected the powder clumpingissue. After about ten layers, the part bin and feed bin temperatureswere set at 165° C. and 122° C., respectively. The tension coupons werebuilt at 20, 25 and 30 watts. The part power setting was 30 watts.

Example A was the best performing of the lots tested. The surfacefeatures were sharp. There was some post-build curling, but this isusually attributed to pulling the parts from the sinter station beforethey have adequately cooled. Overall Example A is considered highlysuitable for selective laser sintering.

Example B

For Example B the feed and part bins were heated to 80° C., which wasabout 5° C. below the reported crystallization temperature (Table 1).The powder spread well, so the temperature was increased in incrementson all bins until 120° C. was reached. The part bin temperature wasslowly increased to 140° C. which was just below the reported meltingpoint. A set of six ASTM D638 tension coupons were successfully run, twoeach at scanning powers of 35, 45, and 55 watts and uniform outlinepower of 5 watts. A second set of six tension coupons were successfullyrun with the same scanning parameters but with an outline power of 10watts. Finally, a third set of six tension coupons were run with 25, 28and 30 watts scanning power and 10 watts outline power. The build wasterminated, and the chamber was allowed to cool prior to removing thespecimens. The part cake was very stiff but removable. It had the lookand feel of angel-food cake. Some smoking occurred at higher powers(45-55 watts), but it did not cause particular concern. The top surfaceof the tension coupons run from Example B was cupped. That is, the crosssection of the tension coupons, instead of being rectangular, had across section with a convex appearance on the top surface. The maximumthickness was approximately 0.17 in, while the minimum centerlinethickness was 0.14 in.

Example B was promising with good processing and good surface finish,though the parts did show cupping. Overall Example B is considered verysuitable for selective laser sintering.

Example C

For Example C the powder tested was coarse and granular. It was loadedinto the chamber and all bins were heated to 85° C. The powder spreadwell so the temperature was increased in 5° C. increments to 140° C.Some “gouging” on the powder feed side was observed occasionally after100° C. This is the maximum temperature for the feed bins. The part bintemperature was increased in 5° C. increments to 170° C. It was thenheated to 172° C., 174° C., 175° C. and finally 176° C. As the reportedmelt point was 174° C. (Table 1), the temperature was not increasedfurther. In an effort to insure that the part bin was not overly caking,the part bin was raised 0.1 in to expose the deposited powder, and theroller was run across the bins. The large amount of part cake behavedlike powder, not a part, so it was concluded that part caking was notexcessive. A build of six ASTM D638 tension coupons was initiated, butthe parts dragged after 3-5 layers due to curling. The part bin layerthickness was increased from the default value of 0.004 in to 0.005 in.On the second layer, the part surface started to pull powder as aninitial start to dragging, so this part build was stopped. The part binwas dropped 0.1 in and was refilled with loose powder from the feed binsto get a fresh start. The part bin temperature was increased to 180° C.(feed bins still at 140° C.). The tension coupon run was initiated, andthe parts seemed to build acceptably at the outset. After about 12layers, short feeding was observed. The feed layer thickness wasincreased from the default 0.015 in to 0.020 in. The six tension couponswere successfully completed, two each at scanning powers of 35, 45, and55 watts and uniform outline power of 5 watts. The part bin was loweredapproximately 0.25 in, and powder was fed from the feed bins to re-levelthe part bin. The part bin temperature was increased to 185° C. with thefeed bin temperature at 140° C., the part bin layer thickness at 0.005in and the feed bin layer thickness at 0.015 in. Powder clumping wasaggravated at the higher temperature due to powder caking. The powderstarted short feeding on Layer 2, so the feed bin layer thickness wasincreased to 0.020 in. The six tension coupons were successfullycompleted, two each at scanning powers of 35, 45, and 55 watts anduniform outline power of 5 watts. The part cake was very stiff butremovable for the first run of tension coupons with the part bintemperature set at 180° C. For analysis of the part cake, one of the two55 watt test coupons was not finished (or tested), so the adherent partcake is present. The six tension coupons run at 185° C. were effectivelycompletely fused to the part cake and were not salvageable. Some smokingoccurred at higher powers (45-55 watts), but it did not cause particularconcern.

Example C was runnable and produced parts that were separable from thepart cake at a part bin temperature of 180° C., though surface finishwas poor. Overall Example C is considered suitable for selective lasersintering.

Molecular weight distributions can be measured on the Waters gelpermeation chromatograph (GPC) equipped with Waters Model 515 Pump,Waters Model 717 autosampler and Waters Model 2414 refractive indexdetector held at 40° C. The GPC conditions may be a temperature of 40°C., a column set of Phenogel Guard+2× mixed D (5u), 300×7.5 mm, a mobilephase of tetrahydrofuran (THF) stabilized with 250 ppm butylatedhydroxytoluene, a flow rate of 1.0 ml/min, an injection volume of 50 μl,sample concentration ^(˜)0.12%, and data acquisition using WatersEMPOWER PRO™ software. Typically a small amount, typically approximately0.05 gram of polymer, is dissolved in 20 ml of stabilized HPLC-gradeTHF, filtered through a 0.45-micron polytetrafluoroethylene disposablefilter (Whatman), and injected into the GPC. The molecular weightcalibration curve may be established with EASICAL® polystyrene standardsfrom Polymer Laboratories.

DSC measurement may be conducted using a Differential ScanningCalorimeter (TA Instruments Q2000 DSC with RCS 90 cooling system). TheQ2000 DSC may be calibrated using the “Heat Flow T4 (mW)” option fromthe Calibration Wizard on the TA Instrument software. It uses an emptycell for the first run, sapphire (clear for the sample side and red forthe reference side) for the second run, then an Indium standard for thethird run. The Cp calibration is done using a sapphire in a Tzero™aluminum pan with lid. The Total and Reversing constants are typicallyset to 1.000 and tested over the temperature range of interest. CpK-values are then calculated and used. This covers both standard modeand modulation mode for the Q2000 DSC. The DSC is calibrated for thetemperature range of interest from −90° C. to 350° C.

Each of the documents referred to above is incorporated herein byreference, including any prior applications, whether or not specificallylisted above, from which priority is claimed. The mention of anydocument is not an admission that such document qualifies as prior artor constitutes the general knowledge of the skilled person in anyjurisdiction. Except in the Examples, or where otherwise explicitlyindicated, all numerical quantities in this description specifyingamounts of materials, reaction conditions, molecular weights, number ofcarbon atoms, and the like, are to be understood as modified by the word“about.” It is to be understood that the upper and lower amount, range,and ratio limits set forth herein may be independently combined.Similarly, the ranges and amounts for each element of the technologydescribed herein can be used together with ranges or amounts for any ofthe other elements.

As used herein, the transitional term “comprising,” which is synonymouswith “including,” “containing,” or “characterized by,” is inclusive oropen-ended and does not exclude additional, un-recited elements ormethod steps. However, in each recitation of “comprising” herein, it isintended that the term also encompass, as alternative embodiments, thephrases “consisting essentially of” and “consisting of,” where“consisting of” excludes any element or step not specified and“consisting essentially of” permits the inclusion of additionalun-recited elements or steps that do not materially affect the basic andnovel characteristics of the composition or method under consideration.That is “consisting essentially of” permits the inclusion of substancesthat do not materially affect the basic and novel characteristics of thecomposition under consideration.

While certain representative embodiments and details have been shown forthe purpose of illustrating the subject technology described herein, itwill be apparent to those skilled in this art that various changes andmodifications can be made therein without departing from the scope ofthe subject invention. In this regard, the scope of the technologydescribed herein is to be limited only by the following claims.

1. (canceled)
 2. (canceled)
 3. An article fabricated by a solid freeformfabrication apparatus, wherein the article comprises fused layers ofthermoplastic polyurethane powder, wherein said powder comprises therection product of (a) a polyisocyanate component, (b) a polyolcomponent, and (c) an optional chain extender component; wherein thethermoplastic polyurethane has a weight average molecular weightmeasured by GPC of less than 150,000; wherein said powder has an averageparticle diameter of less than 150 microns; wherein the resultingthermoplastic polyurethane has a melting enthalpy of at least 10 J/g;wherein the resulting thermoplastic polyurethane has a Tc of at least90° C. wherein the resulting thermoplastic polyurethane has a Tmmeasured by DSC of greater than 170° C.; and wherein the resultingthermoplastic polyurethane has a Δ(Tm:Tc) of between 58° and 71° C. 4.The article of claim 3, wherein the solid freeform fabrication apparatuscomprises: (a) a chamber having a target area at which an additiveprocess is performed; (b) means for depositing and leveling a layer ofpowder on said target area; and (c) means for fusing selected portionsof a layer of the powder at said target area.
 5. The article of claim 3,wherein said solid freeform fabrication apparatus comprises a selectivelaser sintering apparatus.
 6. The article of claim 3, wherein thepolyisocyanate component comprises an aromatic diisocyanate.
 7. Thearticle of claim 3, wherein the polyisocyanate component comprises4,4′-methylenebis(phenyl isocyanate).
 8. The article of claim 3, whereinthe polyol component comprises a polyether polyol, a polyester polyol, acopolymer of polyether and polyester polyols, or a combination thereof.9. The article of claim 3, wherein the polyol component comprisespoly(tetramethylene ether glycol), polycaprolactone, a polyesteradipate, a copolymer thereof, or a combination thereof.
 10. The articleof claim 3, wherein the chain extender component comprises a linearalkylene diol.
 11. The article of claim 3, wherein the chain extendercomponent comprises 1,4-butanediol, 1,12-dodecanediol, dipropyleneglycol, or a combination thereof.
 12. The article of claim 3, whereinthe powder further comprises one or more colorants, antioxidantsincluding phenolics, phosphites, thioesters, and/or amines,antiozonants, stabilizers, inert fillers, lubricants, inhibitors,hydrolysis stabilizers, light stabilizers, hindered amines lightstabilizers, benzotriazole UV absorber, heat stabilizers, stabilizers toprevent discoloration, dyes, pigments, inorganic and organic fillers,reinforcing agents, or any combinations thereof.
 13. The article ofclaim 3, wherein said article comprises cook and storage ware,furniture, automotive components, toys, sportswear, medical devices,personalized medical articles, replicated medical implants, dentalarticles, sterilization containers, drapes, gowns, filters, hygieneproducts, diapers, films, sheets, tubes, pipes, wire jacketing, cablejacketing, agricultural films, geomembranes, sporting equipment, castfilm, blown film, profiles, boat and water craft components, crates,containers, packaging, labware, office floor mats, instrumentationsample holders, liquid storage containers, packaging material, medicaltubing and valves, a footwear component, a sheet, a tape, a carpet, anadhesive, a wire sheath, a cable, a protective apparel, an automotivepart, a coating, a foam laminate, an overmolded article, an automotiveskin, an awning, a tarp, a leather article, a roofing constructionarticle, a steering wheel, a powder coating, a powder slush molding, aconsumer durable, a grip, a handle, a hose, a hose liner, a pipe, a pipeliner, a caster wheel, a skate wheel, a computer component, a belt, anapplique, a footwear component, a conveyor or timing belt, a glove, afiber, a fabric, or a garment.
 14. (canceled)